The demand for computing devices that are powerful yet portable, compact yet fully featured is ever increasing. This trend is particularly evident in the evolution of mobile electronic devices (mobile devices), such as cellular telephones, that now function as telephones, video and audio capture devices, video and audio players, web access terminals, and computers.
As mobile devices grow in sophistication, the variety and sophistication of application software is increasing, thereby turning mobile devices into multipurpose productivity tools. Yet, the usefulness of mobile devices and their applications are limited by the small area available for the user-interface. Traditional cellular telephones, for example, include a simple keypad of fixed configuration. Recently, mobile devices have been released featuring miniature QWERTY keyboards, touch sensitive screen interfaces, and reconfigurable keys.
Traditionally, keypads function by transforming the depression of a physical key into an electrical signal that can be interpreted by the mobile device and its application software. FIG. 1 illustrates a hardware/software architecture of a typical mobile device showing one way that key press events may be communicated to application software. The pressing of a key on a traditional fixed keypad 5 closes a circuit or changes a capacitance or resistance that results in an electrical signal that can be processed by a hardware driver 4. The hardware driver 4 may be circuitry, software or a mixture of hardware and software depending upon the particular mobile device. The hardware driver 4 converts the electrical signal received from the keypad 5 into a format that can be interpreted by a software application running on the mobile device. This signal may be in the form of an interrupt or stored value in a memory table which is accessible by application software. Such an interrupt or stored value in memory may be received by a runtime environment software layer 3. The purpose of the runtime environment software layer 3 is to provide a common interface between application software and the mobile device. Thus, key press event signals are passed on to the application layer 2 in the form of a key press event message. The application software must be able to understand the meaning of the key press event, and therefore must be written to accommodate the underlying hardware driver 4 and keypad hardware 5. Key press events may also be communicated to a user-interface layer 1 such as to display the value associated with a particular key.
Virtual keypads (i.e., software generated keypads on a touch sensitive display surface) provide mobile device designers with increased design flexibility and freedom. By multi-tasking the touch sensitive display surface to act as a keypad only when needed, the mobile device may provide the user with a larger display surface when a keypad is not needed. However, virtual keypads continue to use a traditional approach. That is, virtual keypads typically mimic the function and layout design of traditional keypads.